Roentgen and the Discovery of x Rays

Wilhelm Conrad Roentgen (or Röntgen) was a well-known and accomplished physicist, but he is best known for his discovery of X-rays. This discovery changed medical science, giving doctors a way to look at interior structures of the body without resorting to surgery.

As with many major scientific discoveries, Roentgen’s discovery of X-rays occurred accidentally. On November 8, 1895, Roentgen was conducting experiments that involved passing an electric current through certain gases under low pressure. Earlier, similar experiments by other scientists had led to the discovery of cathode rays. Roentgen’s work was intended to focus on cathode rays, but instead he found something completely different.

Roentgen’s experiments involved enclosing gases in a vacuum tube, then passing electricity through the tube to create a fluorescent light emission. On this particular night, Roentgen enclosed the tube he was using for his experiment in thick, black paper. He was working in a dark room, as well, and discovered that when the electrical charge passed through the gas, a different kind of fluorescent reaction occurred from what he had expected.

Holding a plate coated with barium platinocyanide in the path of the light emitted by the gas, Roentgen discovered the chemical on the plate would produce a fluorescent reaction even as far as six feet away. Intrigued by this phenomenon, he continued his experiments, placing various objects between the tube and the plate. Eventually, he discovered the effects of this light on photographic plates. Objects held between the discharge tube and a photographic plate appeared on the plate in an image that showed different levels of transparency.

Finally, in a history-changing moment, Roentgen placed his wife’s hand in the path of the discharged light and held it immobile to create a photograph. He developed the photographic plate and discovered that he could see her bones within the flesh of her hand, because the light did not pass through them as efficiently as it did through her skin. A ring she was wearing also appeared as a solid object. This picture became the first X-ray.

Roentgen christened these new light rays X-rays because he did not know the nature of the light. He also showed that they were the byproduct of cathode rays striking solid objects. His ability to replicate the phenomenon led to the eventual common use of X-rays in medical and other applications. Later scientists discovered X-rays are simply a different form of light, with a much higher vibration frequency that that of visible light.

Roentgen received the Nobel Prize in Physics in 1901 based on his discovery of the X-ray, but this achievement pales in comparison to the wide-ranging benefits X-rays have brought to the world.